A high-level challenge in networking is the establishment of a global service model abstraction and allowing the service model to operate and be reconfigured while the underlying physical network infrastructure is partitioned (i.e., while portions of the network are disconnected from the rest of the network). Possibly, no majority of failure domains will be available.
In general, routing protocols are able to sustain partitioning. For example, Border Gateway Protocol (BGP) can sustain partitioning even in the presence of independently configured policies. Therefore, in such cases network partitioning becomes a non-issue and the routing state can be expected to converge towards a consistent state.
However, in the case of software-defined networking (SDN), the state model is richer and the control plane is not coupled over the physical topology. As such, handling the partitioning of the underlying physical network becomes more difficult.